Problem: $ { \left[\begin{array}{rrr}{2} & {1} & {-1} \\ {1} & {4} & {-2}\end{array}\right]-\left[\begin{array}{rrr}{-2} & {-2} & {2} \\ {2} & {-2} & {2}\end{array}\right] = {?} } $
Solution: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rrr}{2}-{-2} & {1}-{-2} & {-1}-{2} \\ {1}-{2} & {4}-{-2} & {-2}-{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{4} & {3} & {-3} \\ {-1} & {6} & {-4}\end{array}\right]}$